The first name that came to mind was Sylvie. It's close to the popular Sophie, but it is still unique, easy to pronounce/spell, and not likely to be one of many in any classroom. In terms of nicknames, people will give their own term of endearments to any name, so I feel like nicknames are unavoidable. My DS's name is Bram. You would assume that there would no possible nickname for this one syllable name, but he is constantly called Brammie or Brammer by friends/family members/teachers. It is what it is Good luck with the name search.

4) Nickname distaste. Both of us have a huge distaste for nicknames. The only name we could agree on, Adelaide, had to go out the window because my family insisted on calling her Addie.

I would NOT let your family's nickname tendancies dissuade you from a name you both love and agree on. If you call her Adelaide and only Adelaide, that will be her name, even if grandma calls her "Addy" for a bit, I guarantee it will end especially if you ask "please don't call her Addy" multiple times. For what it's worth, I LOVE the name Adelaide but couldn't get it past my husband for my daughter. We ended up with a "Scarlett" for our first which is pretty nickname-proof. Good luck!